watchOS 5.1 (16R5559d) for Apple Watch Series 4 (40mm) ✗ This OTA is not signed. OTA firmwares cannot be restored to. IPSW Downloads collects them for
potential future use. They might also be useful if you're doing research.
Release Date September 18, 2018 Upload Date September 14, 2018 Filename e98c88e2202495103cfee7652e3e8773fccc78cc.zip Filesize 1.3 GiB Identifier Watch4,1
All information on these pages is automatically updated. When you click on any Apple Software link on
the site, you are redirected to an Apple server. We do not (and never will) mirror these files. All trademarks are the property of their respective owners. IPSW Downloads is not affiliated with Apple Inc.
© 2026 IPSW Downloads
This page was last modified at 1:25:33 pm UTC on Monday, April 6, 2026 and built at 10:20:08 am UTC on Sunday, April 19, 2026.